Abstract:
The potential of algal biofuels has been technically and experimentally confirmed
with laboratory- and pilot-scale studies in past literature. However, the most
important factor now is to confirm that algal cultivation for biofuels and other
end-products is economically feasible on the large, commercial scale. The
ALGADISK project aimed to produce a novel biofilm-based photo-bioreactor
with the aims of CO2 capture and making valuable products such as biofuel,
economically viable. This thesis aimed to investigate and provide substrates in
which algae biofilm is stimulated and increased. Polyelectrolyte (PE) coatings
adsorbed onto cost-effective polymers were investigated, based on the strategy of
electrostatic attraction. It was found that the algae species charge density and cell
wall functional groups composition affected attachment onto charged PE
coatings. Two coatings labeled C1 and C3 were selected due to their promising
growth results with the strains C.sorokiniana, C.vulgaris and S.obliquus.
Harvesting growth results showed inconsistent regrowth due to the lack of
textured structure. Sandpapering the surface with certain grades was found to
improve regrowth and consistency. Surface roughness did not show correlation
to initial attachment of algae or strength of attachment. It was shown instead that
surface roughness improved long-term growth
As part of the aims of the ALGADISK project, the coatings large scale potential
and cost was optimized. It was found that airbrushing rather than dip-coating,
reduced the amount of PE solution needed drastically. Furthermore, photo-cross-
linking with UV exposure enhanced the strength of C1 according to scratch and
wear data.Lastly, the physico-chemical properties of both algae and substrates were
examined in order to examine the thermodynamic model for algae adhesion
prediction. It was found that the two thermodynamic approaches tested did not
predict algae adhesion results with good accuracy. However, it was revealed that
there could be a possible link between the substrate physico-chemistry and lipid
content found in the biofilm attached. It was found that the less favorable the
predicted thermodynamic conditions the higher the lipid content.
